sqlalchemy insert-select from gives error when select clause has zero result

Question

Below is the mwe (assuming session and engine):

metadata=MetaData()
class node(Base):
    __tablename__ = 'nodes_tbl'
    pid = Column(Integer)
    __table_args__ = (
        PrimaryKeyConstraint('pid'),
        {},
        )

for i in range(0,100):
    session.add(node(i)) 

visited_tbl = Table('visited480', metadata, Column('visited', Integer, primary_key=True), Column('level', Integer, p\
rimary_key=False))

metadata.create_all(engine)

#this works                                                                                                          
session.execute(visited_tbl.insert().from_select(['visited', 'level'], session.query(node, sqlalchemy.sql.expression\
.literal_column('1').label('l')).filter(node.pid > 50)))


#this fails; possibly because of zero items                                                                          
session.execute(visited_tbl.insert().from_select(['visited', 'level'], session.query(node, sqlalchemy.sql.expression\
.literal_column('1').label('l')).filter(node.pid > 100)))

The error I get is TypeError: 'NoneType' object has no attribute __getitem__

What is confusing is why is Python showing up between the select and insert statement. Shouldn't it create an SQL and let the DB handle it?

sqlalchemy insert-select from gives error when select clause has zero result

0 Answers0